Dealing with noise may be a significant obstacle in providing an effective hearing aid. Hearing aid users may have difficulty hearing desired audio signals due to electromagnetic interference, acoustic feedback, and various other noise signals. Some types of noise may be annoying and irritating to hearing aid users, and certain noise conditions may even render a hearing aid practically unusable.
Hearing aid manufacturers have implemented various technologies to address noise. For example, some hearing aids may attempt to boost gain in frequency subbands with low noise while reducing gain in frequency subbands with high noise. One problem with this frequency-gain approach is that desired signals may be attenuated along with noise signals. Another problem with many frequency-gain approaches to dealing with noise is the inaccuracy of traditional algorithms for detecting which frequency subbands contain noise. In other words, many traditional algorithms may be somewhat ineffective in distinguishing between noise signals and desired signals.
Frequency-gain technologies and other traditional noise reduction techniques may be particularly ineffective for dealing with certain types of noise. For example, electromagnetic interference within a hearing aid may be picked-up by a telecoil, and such electromagnetic interference may be periodic with a fundamental frequency and numerous strong harmonics. Periodic electromagnetic interference may span numerous frequency bands and may be difficult to address using traditional noise reduction technologies. Other periodic noise signals, such as acoustic feedback, may also be inadequately handled by many prior noise reduction techniques.